If you want to lose fat and keep it off, you must control hunger. The goal needs to be maximal hunger suppression with minimal calories. If you know the science related to hunger and food, then you can accomplish this with ease. Let's begin.
The feeling of filling up from a meal is controlled by hormones and the stretch receptors in the stomach. Both signal the brain that it's time to stop eating. This short-term hunger alleviation is called satiation. Satiety, on the other hand, is the ability to feel full and satisfied over the long-term.
Satiation and satiety have taken a back seat in the nutrition world to things like glycemic index, insulin load, and antioxidant concentrations in foods. This is a shame, because your ability to get and stay full is directly related to your ability to make the right choices at your next meal, and the rest of the day.
What you eat at one meal directly impacts how much you eat, what you'll crave, and how soon you'll want to eat your next meal. Your meals are not mutually exclusive.
Controlling hunger is THE most important aspect of creating a diet that works for you. If you can't get and stay full you'll keep eating, most likely the wrong things, until you do.
Another piece that needs mentioning is satisfaction. The term "satisfaction" is being used here to distinguish between having an empty stomach and brain-related cravings, both behavioral and biochemical.
We all know feeling full doesn't necessarily equate to a desire to stop eating. You can be full, but are you "dessert full?" The desire to taste certain things like sweet, salt, fat, etc., leans more toward a discussion of cravings. Obviously, hunger and cravings are closely linked and overlap significantly.
Are you confused? Even the experts are confused. In the past, I've been part of a panel of experts tasked with finding a "metabolic index" for foods. Basically, we were asked to define the most important characteristics of foods to develop a metabolic ranking system.
Two things became apparent. First, even the experts disagree on the importance of these different factors of nutrition. Second, many of these top experts are woefully misinformed about the science of satiety.
Here is the ultimate point: A healthy, low calorie, nutrient-dense meal is none of these things if, as a result of eating the meal, hunger and cravings for high-calorie junk food occur later. It's critical to understand that what's eaten (or not eaten) at one meal is directly related to what's craved, and how much will be eaten, at the next meal.
Spend just one week in a weight loss clinic and you'll immediately see the futility of prescribing diets based strictly on the health attributes of food. If people don't like what they're eating, and their food doesn't satiate and satisfy them, then they have almost zero chance of success.
Science can go a long way in telling us what's most likely to work, but there has always been, and always will be, individual reactions that contradict the science. This is the art of metabolism, and I encourage you to always honor your individual reactions to food over what the science says. You know your body better than any doctor or research study does.
This info is meant to help you make the decision that taking a "structured-flexibility" approach is in your best interest. The science should be your structure. That's where to begin. But then be flexible in honoring your own body's responses. You may indeed vary from others somewhat since science is about averages, not individuals.
The research is pretty clear on how different macronutrients impact hunger. And this research is falsely communicated by many experts and bloggers! The vast majority of studies show that the hierarchy of macronutrients, in terms of suppressing hunger, goes like this: protein is better than carbs, which is better than fat. (1)
Notice that fat is last, not first. This is not my opinion; this is what the science tells us. I realize this will come as a shock to many people following popular paleo, primal, and keto diets. Fat is the least satiating of the macronutrients. Multiple research studies over years confirm this fact.
Protein reigns supreme as the ultimate hunger fighter. Again, research is very clear on that. There's a little less certainty when it comes to carbs compared to fat. Most studies show carbs are better than fat, but there are more than a few that show the opposite. This likely has to do with fiber content of the carbs studied, as fiber is also very satiating.
So, the data leans very, very strongly towards fat being the worst macronutrient for controlling hunger. Fat contains more than double the energy of an equal amount of protein and carbs, and is also the least thermogenic of the macronutrients.
In other words, in terms of fat-storing potential of macronutrients (meaning, how likely it will contribute to calorie excess and fat gain), the same hierarchy for satiation holds true for fat storage. When single macronutrients are considered, protein is least likely to be stored, carbs next, and fat most.
This becomes more complicated when you consider low-carb diets and ketogenic diets. There's still much debate, but just understand that these diets are almost always higher in protein, and protein and fat are VERY satiating in combination. As a result, these diets almost always end up being lower calorie diets than the diets they're compared to.
Of course, macro combinations matter since we don't typically eat foods in isolation. These combos support the idea that adding either fat or carbs to protein elevates their satiating potential. Additionally, adding fat to carbs increases satiation, but this may not be much help since this combo is very calorie dense AND may cause cravings for more calorie dense foods later.
What about the experts in the paleo, primal, and keto circles who say differently? And what about all the talk about how satiating fat is? Well, almost all low-carb, high-fat diets are higher in protein than the high-carb diets they're compared to.
When protein levels are held constant, the data shows it's the protein content of these diets, NOT the fat content providing the effect. (2) The particular study noted here is one of the few that has looked at this problem by equalizing protein levels in the compared diet.
Another issue is ketones versus fat. Ketones (the fuel you get from the breakdown of fat) may indeed be hunger-suppressing. However, fat and ketones are not the same thing. It takes 10-30 days for the typical person to "keto adapt." At that point, these high-fat diets do seem to become hunger suppressing. That is from the ketones, but again, ketones are NOT fat. They're not a macronutrient.
I'm not aware of any studies looking at the ketone versus protein contribution to satiation once someone has keto-adapted. Given that people will need a protein content below 20% to reach ketosis, and the studies of ketones on hunger that do exist show hunger suppression, we may be able to safely say ketones are on par with protein in their ability to satiate. But this remains an unknown.
Part of the issue with varying effects of carbs may be the amount and type of fiber they contain. High amounts of soluble and viscous fibers are shown to have a powerful hunger-suppressing response.
The fibers that seem to provide the most benefit are viscous in nature. Viscosity refers to the thickness and gel-like nature of the fiber. These types of fiber coat the digestive lining interacting with L & K cells, which then signal, through hormones like GLP and GIP, to turn down hunger.
In fact, a 2013 study showed that viscous fibers may be the only types that do aid hunger suppression. (3) They include things like B-glucan from oats, psylllium, glucomannan, guar gum, and pectins from things like apples. The take-home here is to add fiber as a priority, along with protein, for maximal hunger suppression with lower calorie load.
The goal of any meal should be to fill up quickly (satiation), and stay full for as long as possible (satiety) with the least amount of calories possible. This is why protein and fiber, in combination, may be better than protein and fat or starch.
Now we get to one of the most fascinating, and least talked about, aspects of hunger. It also may be the most important.
Before you even put food in your mouth, you're making assessments and determinations that will impact its ability to satisfy you. Is it liquid? Is it solid? What does it smell like? Is it on a very large plate or a small plate? In what context is the food being eaten? Are you by yourself watching TV, or at the movie theater watching a movie with friends?
One review summed it up this way: "Even before food arrives in the gut, cognitive and sensory signals generated by the sight and smell of food, and by the oro-sensory experience of food in the oral cavity will influence not only how much is eaten at that eating episode (satiation) but also in the period after consumption (satiety)." (1)
Once you begin chewing a food, its texture has a large impact. Solid foods are more hunger-suppressing than liquids. Viscosity, creaminess, and other factors effect how impactful the food will be on hunger as well.
The "mouth feel" of a food is important, and conveys information about the probable nutrient density of the food. This is sometimes referred to as the "cephalic phase response" or the "neuro-lingual response."
In the world of texture and hunger, the hierarchy appears to goes like this:
solids > viscous liquids > creamy liquids > regular liquids
In one study, adding air to amplify volume in a milkshake preload, while keeping calories constant, caused a 12% calorie reduction at the next meal. (4)
These effects of texture and volume may have much to do with the degree of chewing that's necessary. Many studies examined chewing, and it does indeed reduce food intake. The longer you chew a food, the more satiating it becomes.
To drive this discussion home, one more aspect of hunger needs attention: The context of consumption, and the belief about what is consumed. It's clear, through research, that what you believe about a food will determine how that food impacts you.
In one of the most fascinating studies I have ever read, researcher Alia Crum gave participants two milkshakes and then measured their hunger responses including the hunger hormone ghrelin. (5)
One shake was labeled similar to this: "620 calorie indulgent milkshake." The other shake was labeled a lot like this: "120 calorie sensible diet shake."
Sure enough, people consuming the 620 indulgent shake saw a bigger reduction in hunger and their ghrelin levels fell to levels expected with a high calorie meal. The other group saw less hunger suppression and ghrelin didn't respond to near the same degree.
The amazing thing was that the shake was the same in both groups! Only the label and description were different. If that doesn't make your eyes pop out of your head, it should. This tells us there's a lot more going on behind the scenes related to hunger than we know, and food perceptions are not just a small factor, but a huge one.
One interesting thing to note is that the body is smart, and the effects of texture, volume, and perception may not last past a few exposures if the body doesn't get the nutrients it expects. The ideal scenario is to eat foods with the textures, contexts, volumes, and perceptions of being nutrient-dense that are actually rich in nutrition as well.
Obviously, I've picked on fat a little. It's not because I am anti-fat. On the contrary, fat is required, and likely a better bet than carbs for most people (this is debatable). But the science doesn't support the notion that fat is good for hunger.
This concept makes sense in light of the volume, belief, and contextual elements described above. Here's how the Chambers research summed up the findings on fat in relation to carbs on satiety:
"A high fat food will often be smaller in weight (and volume) than a high carbohydrate (or protein) food of similar energy and this difference may affect the timing of the processing of the nutrients in the gut and also consumer beliefs about the likely consequence of consuming that food. That is, people tend to believe a small serving of food will not be enough to satisfy their hunger regardless of the energy it contains and these satiety expectations are thought to play a key role in eating behavior."
Now that we've reviewed all the science, here's what to do:
- Satiation is hunger-suppression in the short term, and satiety is hunger suppression in the long-term. Eat foods that provide both.
- Satisfaction, a term I use to distinguish craving or the pleasure aspects of food from the purely hunger-reducing aspects, is also important. Texture and tastes are important here. Salt, sugar, fat, and starch usually come along in high-calorie foods, yet using enough, but not too much, in cooking may be essential.
- Protein is the king of reducing hunger. Carbs next. Fat last. If you want to reduce your hunger, then amplify protein intake above all else.
- The combination of fat and starch, or sugar, may actually trigger cravings for more highly palatable food, according to some studies.
- Combining macronutrients is more hunger-reducing than single macronutrients. Adding fat to protein, carbs to protein, or fat to carbs is all more satiety-inducing.
- Low carb diets and keto diets are likely hunger-reducing due to the protein content and the generation of ketones, NOT the fat.
- Fiber is a great hunger fighter, but only highly viscous or sticky fibers seem to do the trick. Adding fiber and protein together would seem wise, as doing so provides great hunger suppression with a low calorie load.
- Chew your food for longer, and choose solid calories over liquid ones when possible.
- When taking calories in through liquids, make sure you drink those that have thick, creamy, and airy consistencies.
- Food labeling and perception matter. If you believe a food will fill you up, and it's rich in protein, thickening fibers, and calories, it likely will.
Reading articles like this can be daunting for those who don't love science, but when we know better, we do better. And now you know why choosing foods for hunger suppression is so crucial.
- Chambers L et al. Optimising foods for satiety. Trends in Food Science & Technology. 2015 Feb;41(2):149–160.
- Soenen S et al. Relatively high-Protein or 'low-Carb' energy-Restricted diets for body weight loss and body weight maintenance? Physiol Behav. 2012 Oct 10;107(3):374-80. PubMed.
- Clark MJ et al. The Effect of Fiber on Satiety and Food Intake: A Systematic Review. Journal of the American College of Nutrition. 2013 Jun;32(3):200–211. PubMed.
- Serisier S et al. Increasing volume of food by incorporating air reduces energy intake. J Nutr Sci. 2014 Dec 8;3:e59. PubMed.
- Crum AJ et al. Mind over milkshakes: Mindsets, not just nutrients, determine ghrelin response. Health Psychol. 2011 Jul;30(4):424-9; discussion 430-1. PubMed.